Conventionally fabric is cleaned using water and a detergent composition which is known as wet washing. Surfactants adsorb on both fabric and soil and thereby reduce the respective interfacial energies and this facilitates removal of soil from the fabric.
Alternatively cleaning can be carried out by dry cleaning wherein organic solvents are used for cleaning. Dry cleaning is traditionally an industrial laundering process carried out in a washing machine. The organic solvent helps in the removal of oily soil in the presence of detergents. The particulate soil is largely removed by providing agitation.
Whilst it is desirable to add surfactants to enhance dry cleaning, surfactants are insoluble in the organic solvent. A small amount of water is added to the organic solvent in a dry cleaning process to facilitate surfactant dissolution. Improved oily soil removal is achieved by a small reduction in interfacial tension.
Our earlier-filed co-pending application WO-A-01/90474, published 29 Nov. 2001 discloses a process of cleaning fabric using a cleaning/washing system of at least two immiscible liquid phases with an interfacial tension greater than 5 mN/m, under agitation. The process uses very much reduced levels of conventional detergent surfactants. The system is especially suitable for removing particulate soil.
The process as disclosed in WO-A-01/90474 requires agitation, which may be provided by any suitable means used for domestic laundering or industrial laundering. The invention is especially suitable for use with washing machines.
Manual washing of fabrics and hard surfaces using bars, powders and pastes is a common method of cleaning, especially in developing countries. Detergent compositions in bar form are particularly popular and cleaning is done by applying the bar to the substrate. Further cleaning is done by applying mechanical force by means of a suitable implement like a brush, pouf, etc. Water used for cleaning is poured over the fabric as and when required.
Fabrics are also known to be soaked in a detergent solution and then further cleaned by applying mechanical force.
The methods used for manual washing are time consuming and tedious and require a lot of effort on the part of the consumer. The process also requires a large amount of water (for cleaning and rinsing), a resource that is not always readily available in developing countries. Further, the cleaning obtained is often not completely satisfactory, in particular as regards the removal of particulate soil.
Hence there has been a need to develop a simple method of manual cleaning that gives good detergency, in particular for particulate soil, does not require large quantities of water and provides for good cleaning with less effort than required in current manual cleaning using detergent products.
Cleaning systems, as disclosed in WO-A-01/90474, give enhanced detergency, in particular for removal of particulate soil. The cleaning systems can be used for manual washing of substrates. As in conventional manual cleaning, washing can be carried out by pouring the two liquids separately on the substrate and then cleaning the substrate by means like brushing. However, the mixing of the two liquids is poor and the liquids are likely to separate quickly under gravity resulting in impaired cleaning.
It is also possible to carry out manual cleaning by mixing the two immiscible liquids by agitation prior to pouring on to the substrate or by introducing the fabric into the mixture and then agitating the same. However, the mixture must remain stable for a few seconds after agitation of the mixture and prior to subsequent steps like rinsing in order to provide for cleaning. This can be achieved by adding surfactants; however, this will reduce the interfacial tension. Further, not all cleaning systems disclosed in WO-A-01/90474 provide for mixtures of immiscible liquids that are stable for a short period of time before carrying out further operations like rinsing etc.
We have now found that the above drawbacks can be overcome to a significant extent by using a cleaning/washing composition comprising two immiscible phases having a high interfacial tension wherein the density of the two immiscible phases is the same or similar. The cleaning/washing composition of the invention is stable after agitation and gives good detergency, in particular for particulate soil. A process for cleaning using the cleaning compositions of the invention is also provided for. It is required that the cleaning composition be suitably agitated before or after contacting with the substrate. Subsequent to cleaning, friction is applied to the substrate by rubbing, by means of a brush, pouf, sponge or any other means known in the art. Advantageously, the process uses less water than conventional detergent systems for manual cleaning.